Two girls get swept up in a murder mystery in their small town.It's a hot summer, and 12-year-old Abbi and her best friend, Skylar, spend their days at the mall, the pool, and the library. When Skylar, the more daring of the duo, decides they should bike to the edge of town, a seedy area where the bullies from their school live, Abbi has reservations but says yes anyway. The discovery of a treehouse makes the journey worthwhile, and things become even more interesting when they spot a mysterious man and woman meeting up just below. Are they Russian spies like Abbi imagines or just regular adults having an affair like Skylar's dad did? The fun mystery turns serious, though, when the woman runs off into the menacing woods. When a beloved teacher goes missing, the friends piece together the information and have to figure out how to help without winding up in trouble with their parents, or worse. The prolific Hahn, particularly known for her eerie ghost stories, stays away from the supernatural in this quick-paced tale but keeps the thrills coming. She expertly captures the feel of a small-town summer and tumultuous middle school friendships and never talks down to young readers or shies away from frank descriptions of real-world threats. Still, an optimistic ending shows there is always light and joy to be found. The protagonists are cued White.A chilling and thrilling addition to a beloved author's oeuvre. (Thriller. 9-13)